In a number of instances, laser scribing and welding processes are used in the fabrication of thin film semiconductor devices. These devices may comprise photovoltaic devices as well as other devices such as photodetector arrays, electrophotographic components, integrated circuits, and the like. In the context of this disclosure, the invention will be explained primarily with respect to the fabrication of thin film photovoltaic modules; however, it is to be understood that the principles disclosed herein are applicable to other types of semiconductor devices. In the fabrication of thin film photovoltaic modules, a series of scribing and laser welding steps are utilized to configure various electrode and semiconductor layers into an array of individual cells which are interconnected in a series and/or parallel relationship.
Such laser fabrication processes are precise and quick; and hence, such techniques are very often used in the fabrication of photovoltaic modules and other semiconductor devices. Some such laser fabrication processes are shown in U.S. Pat. Nos. 6,767,762; 5,268,037; 6,011,215 and 5,468,988. Typically such devices of the prior art are fabricated on relatively thick substrates such as sheet metal or glass. However, there is growing interest in the fabrication of ultra lightweight semiconductor devices, and in particular ultra lightweight photovoltaic devices. In general, lightweight photovoltaic devices are understood to be devices producing upward of approximately 1,000 watts per kilogram of weight and ultra lightweight photovoltaic devices are understood to be capable of producing upwards of approximately 2,000 watts per kilogram of weight. Such ultra lightweight devices are fabricated on thin, flexible substrates which can include polymeric materials such as polyimides. Problems occur when laser fabrication techniques are utilized in connection with such ultra lightweight devices, since the substrates themselves typically absorb most commonly employed laser wavelengths. Furthermore, the ultra lightweight substrates have a very low thermal mass. As a result, laser processing techniques can cause thermal damage to the substrates as well as to semiconductor and electrode layers supported thereupon. Hence, the advantages of laser fabrication technology have not been, heretofore, successfully applied to the manufacture of thin film, ultra lightweight semiconductor devices.
As will be described hereinbelow, the present invention provides methods, systems and apparatus which may be utilized to adapt laser technologies to the fabrication of ultra lightweight photovoltaic modules and other semiconductor devices.